Chromosome Theory of Inheritance

The Chromosome Theory of Inheritance, also called the Boveri-Sutton chromosome theory, is a theory which was created by German scientist Theodor Boveri and American scientist Walter Sutton, which identifies chromosomes as the carrier of genetic material. Boveri and Sutton were students of Gregor Mendel, and they sought to apply his study of passing off traits to offspring while thinking about the process. They also sought to discover the process by which heritable factors were passed down from parent to offspring; the variation of genes, known as alleles, are present in each cell, and Mendel discovered that they were passed on from parent to offspring. The alleles are segregated, with a parent passing on either a dominant gene (A) or a recessive gene (a), the Law of Dominance. Either way, it was independent from whether the other gene, "B" or "b", was passed down, the Law of Independent Assortment. Mendel had no idea as to how the process happened at a cellular level, but, with the invention of microscopes, Boveri and Sutton began to independently study the process from 1902 to 1903. They believed that chromosomes were the cellular mechanism by which the genetic factors segregated and independently assorted, and they attempted to research this through studying sea urchins and grasshoppers, respectively. They also sought to discover what was inside the chromosomes which allowed for the traits to be passed down. The process began with homologous chromosomes (which are similar in length, size, and shape, but they are different chromosomes), with one of the chromosomes having what encodes for the gene "A", while another chromosome encoded for the other gene "a". Through the process of meiosis, the chromosomes segregate and independently assort, with each newly produced cell having half of the original chromosomes. The scientists discovered that the chromosomes carried the heritable factors, discovering that the cells carried the parents' chromosomes and data, and that the passage of these meiosis products (gametes) would allow for humans to sexually reproduce and pass down traits.